McLaren hit the jackpot with the exclusive Senna supercar. Not only the street version was very popular, but also the circuit one. The McLaren Senna GTR, a track-only hypercar that debuted in concept form at the Geneva International Motor Show in March 2018 and sold-out in the same month, begins dynamic testing this month.

McLaren tested demand for the track-only, left-hand-drive only car on its introduction at Geneva, saying that up to 75 would be produced. Many more expressions of interest were received, but the company has confirmed that only 75 will be available, all of which are already allocated. Deliveries are expected to begin from September 2019 when production of the road-legal McLaren Senna is complete.

The development prototypes that begin testing this month will initially use modified Senna road car bodywork. The final Senna GTR shape – shown in simple form in a new design sketch – will be based around a chassis with wider track front and rear and centre-lock wheels.

The carbon fibre body has new, wider fenders, a larger front splitter and rear diffuser and repositioned active rear wing; these last two elements combining to improve aero-efficiency by ‘coupling’ the wing to the airflow from the diffuser, enabling greater – and more accessible – downforce at lower speeds. Optimised aerodynamic performance in yaw improves cornering stability, while reduction in pitch sensitivity leads to even greater braking stability.

A final vehicle weight is still to be declared, but the GTR will weigh less than the road-going Senna. In combination with the 825PS output of the 4.0-litre twin-turbocharged V8 engine – an increase of 25PS over the road-legal Senna – this will see the power-to-weight ratio comfortably exceed that of the road car. Together with torque of up to 800Nm, the result will be astonishing levels of response and performance.

The Senna GTR retains the active aerodynamics of the road-legal car – an advantage that would not be permissible in a homologated race car – which is a major enabler in generating the 1,000kg of downforce. The car has conventional double wishbone suspension, with the geometry, springs, dampers and anti-roll bars having been developed from the system engineered for McLaren’s GT3 customer racing programme. Pirelli slick race tyres maximise dynamic performance and the braking system – introduced in the Senna road car and also race-derived – is projected to deliver 20% greater maximum deceleration, with resulting forces in excess of 3g.